Why not have them painted and then take them to your dealer and have him install them? Installation is included in the GFX Rpo.

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1100, Preliminary order accepted 12/5
2000, Order accepted by GM 05/05
3000, Order accepted by production control 05/05
3400, Order broadcast 6/4
3800, Order produced 6/15
4000, Available to ship 6/16
4104, Bailment Invoice
4200, Shipped 6/19
6000, Delivered to the customer 6/25

Even if something does need drilling....would you rather have a stranger do it than do it yourself? I think not...
If any holes had to be drilled I know that I would be using a good sealant on all the threads and the area around the hole and screw in en effort to prevent rust later. I doubt that an installer would do anything like that if it does not specifically say to do it in the install instructions. It would subject him to civil liability later if he did anything differently than the instructions say to do it.
Its like my father always told me..."why pay somebody to screw something up when you can screw it up yourself for free".